Toggle mechanism for mercury switch

ABSTRACT

A mercury switch includes an insulating housing attached to a strap for mounting the switch in a wall box. The housing contains contact strips communicating with the insulating housing exterior and a mercury button mounted in pivoting relation between internal portions of the strips. Pivoting is actuated by a toggle mounted against the mercury button and having an externally extending trigger for control of the button pivot position from the switch exterior. Trigger movement is made smooth by an improved toggle mechanism including a longitudinal spring bearing at its ends against the underside of the strap and at its midportion against turnions of the toggle. The longitudinal spring also compensates for small dimensional differences of elements of the switch and provides lateral stability to the trigger.

iJnited States Patent 11 1 Schumacher TOGGLE MECHANISM FOR MERCURY SWITCH 1451 Sept. 11,1973

Primary Examiner-Herman J. Hohauser Att0mey-Paul E. Rochford et al.

[57] ABSTRACT A mercury switch includes an insulating housing attached to a strap for mounting the switch in a wall box. The housing contains contact strips communicating with the insulating housing exterior and a mercury button mounted in pivoting relation between internal portions of the strips. Pivoting is actuated by a toggle mounted against the mercury button and having an externally extending trigger for control of the button pivot position from the switch exterior. Trigger movement is made smooth by an improved toggle mechanism including a longitudinal spring bearing at its ends against the underside of the strap and at its mid-portion against turnions of the toggle. The longitudinal spring also compensates for small dimensional differences of elements of the switch and provides lateral stability to the trigger.

4 Claims, 5 Drawing Figures 1 TOGGLE MECHANISM FOR MERCURY SWITCII CROSS-REFERENCE TO RELATED APPLICATION This application relates to application Ser. No. 248,407 filed Apr. 28, 1972 Attorneys Docket No. 58WD-l064 of Ralph L. Graves and Walter C. Schumacher and owned by the assignee of this application.

BACKGROUND OF THE INVENTION Mercury buttons and switches have been known formany years. A number of such buttons and switches are well known in thepatent literature and within the past years a number of patents have issued to the owner of this application describing improvements in such buttons and switches. These patents include: US. Pat. Nos. 2,916,589; 2,929,902; 2,956,656; 3,032,633; 3,109,079; 3,089,937; 3 ,229,354; 3,265,844; 3,327,084; 3,415,965.

Mercury switches are well known for certain performance characteristics including long operating life and quiet operation. In fact most mercury switches are essentially silent in their on-off operation as contrasted with switches operating byjoining and separating solid contacts which are more properly characterized as quiet rather than silent. Moreover, the movement of the trigger of mercury switches is,-very smooth from full ON to full OFF as there is no overcenter drive of the trigger to an at-rest position to produce a snap or click as the switch is operated. r

One problem which is encountered Y in mercury switches is that of limiting the cost of manufacturing the switchesso that they will befavailable to the purchasing public at reasonable prices. Thelimitationof switch cost includes both preparationiof partsand the assembling of these parts into a completed switch struc:

ture.

SUMMARY OF THE INVENTION It is accordingly one object of the present invention to provide a mercury switch having a smooth trigger action. 6

Another objectis to facilitate reliable assembly of a mercury switch.

Still another object is to provide a low cost mercury switch having smooth trigger operation and a long reli-. able operating life. z

' The present invention in one embodiment thereof provides a toggle mechanism for mercury switch having an insulating housing attached to a mounting strap for mounting the switch in a wall box. The mercury switch also has a mercury button mounted within said housing in pivotable relation. 7

A toggle has a body conforming to the mercury button, a trigger, and trunions. The toggle body embraces the mercury button and permits controlled pivoting of the button by movement of the trigger extending from the housing through the strap. Two parallel leaf springs are disposed between the trunions and the undersurface of the strap to apply spring bias to the trunions as the toggle is pivoted.

The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent, and the invention itself will become more fully understood by reference to the following description, taken in conjunction with the accompanying drawings, wherein BRIEF DESCRIPTION OF THE DRAWINGS elements of a toggle mechanism as provided pursuant to the present invention.

Referring now to the drawings there is shown a wiring device, more particularly in the exemplification a switch 10 in this case a mercury switch. For purposes of illustrationthe switch is shown in its conventional formhaving a strap 12 having mounting screw holes 14 and breakoff plaster ears 16. A central portion of strap 12 has a trigger hole-'18 and bridge portion 20 along each side of trigger hole 18. Trigger 22 extends through trigger hole 18 'fro m-the'switch interior."

A,rectangular spring 47 isshown in phantom extending around trigger 22 and the trigger hole 18, and particularly beneath bridge portions 20. t

The conventional insulating housing-24 of the switch has a screw terminal :28 with screw 26 for fastening power supply wires'to' the switch. Y 'Within the switch a'contact strip 30 communicates with terminal 28 and extends along one internal side of the insulating housing 24. Another strip not shown extends along the other internal side of the switch and communicates with a screw terminal not shown located cater-comer to terminal 28 on the insulating housing 24.

Mercury button 32 shownpartly in phantom is held in housing 24 between the contact strip 30 and its oposite member not shown. One side of button 32 nests in the conforming button grip portion 34 of a toggle 36 and'pivots to match the pivot ofthe toggle. induced by movement of trigger 22. g

The other side of button-32 rides on cradle support 38 a boss formed integrally as part of insulating housing 24 and having a circular track confronting and conforming to the circular shape of .button 32. As the button 32 pivots in cradle 38 it can undergo no in-and-out motion relative to itscradled support within the insulating housing 24 as this support, as well as the button, are rigid. a

The toggle 36 is also a'rigid body and its conforming b'utton grip -portion 34 is in close conforming contact with the button32. The button grip portion 34 has a boss 40 conforming to notch 42 in button 32 providing a grip of the toggle on the button so that the button is pivoted in responseto movementof trigger 22.

For convenienceof reference a direction into the switch housing toward the cradle 38,is referred to as down or under, and a direction toward the strap is referred to as up or over.

The toggle 36 pivots about the center of button 32 and as it does so trunions 44 extending laterally from the toggle contacts pair of leaf springs 46 arranged on either side of the toggle.

The leaf springs shown are joined at their ends by cross pieces 48 so that proper alignment of leaf springs 46 is facilitated in assembly of the switch, in other.

words the single rectangular leaf spring element 47.

The leaf springs 46 are held in place against the trunion 44 by the strap 12 and particularly by the land 50 at each end of trigger opening 18. The central sections 52 of springs 46 normally do not contact the underside of bridge section 20 of strap 12. Rather the trunion 44 bears against the central section 52 and is held in place in relation to button 32 and housing 24 under spring bias developed by this contact.

The manner of contact of various portions of trunion 44 with the central sections 52 of leaf springs 46 results in a very smooth trigger action as well as a soft stop at the end of the trigger stroke.

The manner in which this is achieved is evident from consideration of the elements of trunion 44 in relation to springs 46 as best illustrated in FIGS. 3, 4, and 5.

The trunion 44 has three principal portions, a generally flat bearing surface 58 at one side and another 54 at the other, and a curved crest 56 therebetween. Each flat bearing surface when in flush contact with leaf spring 46 is the at-rest contact position for the trigger in either the ON or the OFF position for the switch.

As the trunion moves from one at-rest position with a flat bearing surface against spring 46 to the other atrest position, its crest 56 comes into contact with the spring and deflects the spring outward toward bridge portion 20 of strap 12. This outward deflection results because the bearing surfaces of crest 56 are further from the center of rotation than either flat sections 54 or 58. The slight increase of spring pressure during the travel of trigger'22 as the crest 56 starts to bear against spring 46, and the slight release of spring pressure as the trunion arrives at the other at-rest position gives the trigger movement a very smooth feel to the fingers of an operator and a general resemblance to the trigger motion of overcenter switches. It is thus possible to tell from the tactile sensing when the switch has arrived at the ON or OFF positions even in a darkened room.

A soft stop is provided at the end of the trigger stroke to either the ON or OFF position also by a cooperation of the trunions 44 with the springs 46. This is illustrated best in FIGS. 3 and 4 where the trigger is shown in each case in the-overstressed position which gives rise to the soft stop of the trigger. 1

Referring first to FIG. 3 the trigger 22 is shown at the lowest point in its travel to and past the at-rest OFF position. When at the at-rest position flat bearing surface 54 is in flush contact withthe central section 52 of leaf spring 46. A similar flat bearing surface in flush contact with the central section of the other leaf spring not shown on the opposite side of the switch provides a balancing spring bias on the other trunion of toggle 36.

After the toggle moves to its normal at-rest position a stop surface 60 under flat bearing surface 54 comes into contact with upper surface 31 of contact strip 30. As the toggle moves to the opposite position shown in FIG; 4 the stop surface 62 under flat bearing surface 58 comes into contact with another portion of the upper surface 31 of contact strip 30.

Similar contact of similar trunion stop surfaces with the upper edge of a similar contact strip (not shown) on theother side of the switch occurs at the same time that strip 30 is contacted.

As the trunion stops at the strip edge it is lifted slightly as its bearing surface comes into closer and more forceful contact with spring 52.

As trigger 22 is moved past a full at-rest position to' that shown in FIG. 3 the outer end 53 of the flat bearing surface 54 bears increasingly against and deflects central section 52 of spring 46. As this deflection :occurs the movement of trigger 22 is quickly decelleratcd as increasing bias is developed in the spring. If the: movement of trigger 22 is very forceful the decelleration of trigger as the spring 46 is deflected is followed by a complete stop as the spring is bowed all the way out into mechanical contact with the underside of bridge 20. However, because of the deceleration under the influence of spring 46, any contact with the underside of bridge 20 is only after motion of the contact has been softened by the cushioning effect of the spring com pression.

in normal use the application of a normal finger force to the trigger will result in a cushioning of the trigger movement with no contact between spring 46 :and underside of bridge 20. This normal cushioning is what the toggle mechanism is designed to provide so that the operation of the switch may remain essentially silent both during movement of the trigger through its normal course and at the decelleration and stopping.

Conversely when the toggle mechanism of this invention is used to turn the switch to the ON position a combination of trigger and trunion motions-and spring contact and deflection occurs which is essentially the same as thosewhich are described above for'turning the switch meteors position.

Normally the upper trunion bearing surfaces 54, 56, and '58 are in contact with the: under surface of leaf spring 52. When at the fullON position the. uppertrunion surface 58 is in contact with spring 52 but the lower trunion surface 62 isjnot in contact with the upper. edge surface 31 of contact strip:30. Only when the toggle is moved into stressed position beyond the full ON or full OFF at-rest positions is an underside of the trunion brought to bear mechanically against upperedge 31 of contact strip 30. Smooth operation between full ON and full OFF is assuredby the constant contact of the upper'bearing surfaces 54, 56, and 58"of the trunion with spring 52.

What is claimed as new and desired to be securedby Letters Patent of the UnitedStates is:

l. A toggle mechanismfor amercury switch which comprises an insulating housing a mercury button, said mercury button being mounted .within said housing in pivotable relation,

a toggle, said toggle having a body conforming to and embracing said mercury button,"

atrigger, said trigger extending out from said. body of said toggle away from said mercury button,

at least one laterally extending trunion being integral with vsaid trigger, said trunion having on its upper side two generally flat sections separated by a crest therebetween,

a strap having a trigger opening mounted to said insulating housing and said trigger extending throughz and said strap having a bridge on at least one side of said trigger opening, said leaf spring bearing downward at its mid-section against said trunion and said and are joined by integral cross members.

4. The toggle mechanism of claim 1 in which the underside of said trunion acts on an element of said switch as a stop as said upper side of said trunion acts on said leaf spring. 

1. A toggle mechanism for a mercury switch which comprises an insulating housing a mercury button, said mercury button being mounted within said housing in pivotable relation, a toggle, said toggle having a body conforming to and embracing said mercury button, a trigger, said trigger extending out from said body of said toggle away from said mercury button, at least one laterally extending trunion being integral with said trigger, said trunion having on its upper side two generally flat sections separated by a crest therebetween, a strap having a trigger opening mounted to said insulating housing and said trigger extending through said opening, a leaf spring, and said upper surface of said trunion bearing against said leaf spring, and said strap having a bridge on at least one side of said trigger opening, said leaf spring bearing downward at its midsection against said trunion and said leaf spring bearing upward at its ends against said strap.
 2. The toggle mechanism of claim 1 wherein two said leaf springs are joined at their ends by cross elements.
 3. The toggle mechanism of claim 1 in which two leaf springs are formed from a single sheet of spring metal and are joined by integral cross members.
 4. The toggle mechanism of claim 1 in which the underside of said trunion acts on an element of said switch as a stop as said upper side of said trunion acts on said leaf spring. 